Thesis (MSc (Agric) (Conservation Ecology and Entomology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Ambient temperature plays a key role in insect-physiology, -population dynamics and
ultimately -geographic distribution. Here, I investigate the survival of codling moth, Cydia
pomonella (Linnaues) (Lepidoptera: Tortricidae), which is a pest of economic importance in
pome fruit production, to a wide range of temperature treatments. In this thesis, I first explore
how temperature affects the survival and limits to activity of codling moth and secondly
investigate if thermal acclimation can improve field performance of moths used in sterile
insect technique control programmes under ecologically relevant conditions. First, I found
that absolute temperature as well as the duration of temperature exposure significantly affects
adult C. pomonella survival. Lethal temperatures, explored between -20 °C to -5 °C and 32 °C
to 47 °C over a range of durations, showed that 50% of the adult C. pomonella population
killed at -12 °C and at 44 °C after 2 hrs for each treatment. At high temperatures a pretreatment
at 37 °C for 1 hr dramatically improved survival at 43 °C for 2 hrs from 20% to
90% (p<0.0001). Furthermore, high temperature pre-treatments (37 °C for 1 hr) significantly
improved low temperature survival at -9 °C for 2 hrs. In sum, my results suggest pronounced
plasticity of acute high temperature tolerance in adult C. pomonella, but limited acute low
temperature responses. Secondly, low-temperature acclimated laboratory-reared moths were
recaptured in significantly higher numbers (d.f. = 2, χ2 = 53.13 p<0.001), by sex pheromone
traps, under cooler conditions in the wild relative to warm-acclimated or non-acclimated
moths. However, these improvements in low temperature performance in cold-acclimated
moths came at a cost to performance under warmer conditions in the wild. This novel study
demonstrates the importance of thermal history on C. pomonella survival and clear costs and
benefits of thermal acclimation on field and laboratory performance, and thus, the potential
utility of thermal pre-treatments for improved efficacy in the sterile insect technique
programme for C. pomonella control under cooler, springtime conditions. Finally, on a global
scale, this study highlights that low and high temperatures could play a role in CM adult
survival through direct mortality and thus, may influence, or have influenced in the pest,
population dynamics. / AFRIKAANSE OPSOMMING: Temperatuur speel ‘n belangrike rol in die fisiologie, populasiedinamika en geografiese
verspreiding van insekte. In hierdie tesis ondersoek ek die rol van ‘n wye reeks temperature
op die oorlewing van kodlingmot Cydia pomonella (Linnaues) (Lepidoptera: Tortricidae), ‘n
sagtevrug pes-spesie van ekonomiese belang. Ek ondersoek hoofsaaklik die effek van
temperatuur op die fisiologie en fiksheid van kodlingmot, asook die mate waartoe termiese
akklimasie (‘n mate van aanpassing) die veldgedrag van die steriele insek beheer-metode
(SIT), d.m.v. kodlingot, in relevante omgewingstemperature kan verbeter. Ek het (i) gevind
dat die temperatuur en duur van die temperatuur toediening ‘n betekenisvolle toename in
volwasse C. pomonella oorlewing tot gevolg het. In die deel van die studie is temperature
tussen -20 °C en -5 °C and tussen 32 °C en 47 °C ondersoek oor ‘n reeks van 0.5, 1, 2, 3 en 4
ure van duur. In kort lei -12 °C en 44 °C vir 2 uur onderskeidelik tot die uitsterf van 50% van
die volwasse C. pomonella populasie. Indien die motte vooraf gehou is by 37 °C vir ongeveer
1 uur, is oorlewing by 43 °C vir 2 ure betekenisvol verbeter van 20% tot 90% (p<0.0001).
Hoër temperatuur vooraf-blootstellings (akklimasie), by 37 °C vir 1 uur, het daartoe gelei dat
lae temperatuur lae-temperatuur-oorlewings by -9 °C vir 2 ure betekenisvol verbeter het. Oor
die algemeen het die resultate gedui dat hoër akute temperatuurstoleransie in C. pomonella
bestaan, maar beperkte akute lae-temperatuur reaksies bestaan. Verder het lae-temperatuur
akklimasie (laboratorium geteelde) motte ‘n betekenisvolle hoër getal hervangste deur
geslagsferomone in koeler omgewings opgelewer (v.i. = 2, χ2 = 53.13, p<0.001) in
vergelyking met warmer-temperatuur geakklimatiseerder motte. Hierdie verbeteringe in laetemperatuur
reaksies vanaf lea-temperatuur akklimasie groepe is teen ‘n koste teen warmer
reaksie-toestande in die natuur geïs. Hierdie eersdaagse studie demonstreer die belang van
historiese temperatuur op die oorlewing van C. pomonella. Die kostes- en voordele van
termiese akklimasie op veld- en laboratoriumpopulasie reaksies en die potensiële gebruik
daarvan in die verbetering van steriele insek tegniek programme, onder koeler
omstandighede, is uitgelig. Laastens, beklemtoon hierdie studie die belangrikheid van
temperatuur as bepalende faktor van kodlingmot-oorlewing en die invloed daarvan op die
vrugte-pes populasiedinamika.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/5375 |
| Date | 12 1900 |
| Creators | Chidawanyika, Frank |
| Contributors | Terblanche, J. S., University of Stellenbosch. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 108 p. : ill., maps |
| Rights | University of Stellenbosch |
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